The present invention concerns a new acidic polycyclic ether antibiotic having the formula: ##STR1## wherein Me.dbd.CH.sub.3, having absolute stereochemistry as shown; pharmaceutically acceptable cationic salts thereof; nutrient feed compositions comprising said antibiotic for poultry, cattle or swine; its use as an anticoccidial agent in poultry, in the treatment or prevention of swine dysentery, or as a growth promotant in cattle or swine; a fermentation method for its preparation; and the Actinomadura sp. microorganism which produces said antibiotic in said fermentation method.
The compound (I) is a new member of the acidic polycyclic ether group of antibiotics. This family includes such well known agents as monensin (The Merck Index, 10th Ed., Merck and Co.,Inc., Rahway, N.J., 1983, monograph no. 6100), nigericin (loc. cit., monograph no. 6390), narasin (loc. cit., monograph no. 6271), lasalocid (loc. cit., monograph no. 5204), and salinomycin (loc. cit., monograph no. 8193). The subject has been reviewed by Westley, "Polyether Antibiotics", Adv. Appl. Microbiol., vol. 22, pp. 77-223 (1977). Most closely related structurally to the present compound is portmicin, an antibiotic independently reported by Hamill et al , U.S. Pat. No. 4,582,822 and by Kusakabe et al., European patent application 158,179; Tetrahedron Letters, vol. 28, pp. 3357-3360(1987); J. Antibiotics, vol. 40, pp. 237-238(1987). The latter compound possesses an alpha-hydrogen on the tetrahydrofuran B-ring where the present compound possesses an alpha-methyl group. These compounds are generally known as coccidiostats, as feed additive-growth promotants, and/or as agents useful against swine dysentery.